Common\Mailer\Message::parseHtml PHP Method

    public function parseHtml($template, $variables, $addUTM = false)
    {
        $html = $this->getTemplateContent($template, $variables);
        $html = $this->relativeToAbsolute($html);
        $html = $this->cssToInlineStyles($html);
        if ($addUTM === true) {
            $html = $this->addUTM($html, $this->getSubject());
        }
        $this->setBody($html, 'text/html');
        return $this;
    }